Typical electrosurgical procedures, such as cutting or cautery procedures, are performed with a hand held device, which the user can manipulate as the RF energy is delivered in order to facilitate the creation of the desired effect at the electrode. The ability to visually see the electrode and to change the proportion of the electrode that is held in contact with the tissue allows the user to adjust the motion or position of the device with respect to the activity observed at the electrode to compensate for the constant power output of a commercial electrosurgical generator and to force the generator to achieve the desired effect. With a percutaneous procedure, in particular an automated, percutaneous procedure, this type of user-based control is not possible, since the electrode is, in many cases, not visible. And in the case of automated control, the effects occur too quickly to allow human reaction. In this case, it is advantageous to have an automated method to evaluate the effect at the electrode and a method to determine when specific events have occurred and initiate the appropriate action. Of specific concern in a procedure requiring the cutting or excision of tissue is the creation of an arc at the electrode, since an arc permits the vaporization of tissue, which is the phenomenon that creates the cut.
For manual systems, where the cutting loop is deployed and rotated by hand by the user, other problems exist. The user may not know if the electrode movement is too slow, which leads to too much RF energy exposure that can result in excessive thermal damage and/or vaporization of the intended tissue sample. If, on the other hand, the electrode movement is too fast, this could result in a weak cutting arc or total loss of the cutting arc, which could result in undersized or mechanically damaged specimens.
This invention utilizes the measurements of the electrical characteristics of the tissue and correlates them to a physical effect at the electrode, which is then used to signal the user to make appropriate adjustments in the method.